This invention pertains to the field of automatic telecommunications devices which operate over telephone lines. More particularly, this invention pertains to the use of automatic telecommunication devices on telephone lines on which normal voice conversations can also occur, and in which ringing, including any abbreviated ringing, of the telephones is inhibited when a connection is made for automatic telecommunications.
There are a large number of applications in which it is desirable to install automatic data collection and reporting devices in a remote unattended site. These devices typically report to a central computer system using some form of telecommunications modem. It is generally more desirable to install this equipment on a switched network telephone line rather than a permanently dedicated leased telephone line. Whenever possible, it is economically preferable to use an existing voice telephone line rather than install a special telephone line for the sole use of this equipment.
However, sharing a telephone line between normal subscriber usage and automatic machine usage can create some special problems. In particular, the presence of the automatic equipment should not impact on normal usage of the telephone line for voice communications. One problem that can and does occur in initiation of automatic telecommunications, in which a central station dials a modem connected to the telephone voice line, is that an abbreviated ringing of the telephones connected to the telephone voice line results. This can occur if the modem does not go off-hook soon enough or if there is a delay in ring trip at the telephone central office after the modem has gone off-hook, which results in abbreviated ringing of telephones on the line.